Pretty much, the MODEL says that the low angle stays the same, and you fill
in the high angles. No loss to DX. Why bother?
According to NEC4, my antenna plays better than it should. One of the
interesting, unprovable antenna theory gut lurches is that moving a current
center high makes the "higher placed" RF less susceptible to absorption by
clutter in the area. In my NE direction take off at 5 degrees, from the
ground, the RF is subject to penetrating a THOUSAND feet of woods. From 95
feet in the air the RF is subject to almost NONE.
How to prove that to standing-man-with-meter? No way. The difference is
clearly up in the air. Whatever difference might be seen at the ground
will be forever bothered by decidedly arguable technical low to ground
issues that are anything but settled. So we go to
sitting-man-with-meter-in-helicopter. How do you prove that the woods had
attenuation at skywave angles? You create the commercial version and the
high-placed current max version on the ground and then you cut down the
woods, with sitting-man-with-meter-in-helicopter measuring all the time.
Over my wife's dead body, and my neighbor's, and my neighbor's, and my
neighbor's, with this little inconvenience of the Wake County Sheriff's
Deputies. Ain't gonna happen.
If you add this absorbative local clutter factor to PROVABLE losses in real
estate confined chop-job come-down radials, where the radiation center is
AT THE GROUND, you create the kind of monster losses that truly explain
some of the is-my-coax-connected-to-the-antenna anecdotes that I hear
repeatedly.
On 80 meters an up 67 out 67 foot halfwave L end-fed with a tank circuit
at the base, against simply pathetic ground, has always been the equal of
an inverted vee supported by a typical 50,60, 70 foot-ish tower at the
local level. For DX the end-fed half wave L was always superior.
The models specifically say cannot be in their model universe. But in
reality the models are wrong. The models don't match RBN numbers.
However I have not been spending any time on that argument on 80. This
little thing called FCP has me fairly well occupied.
The real shortage for the 80 end-fed half wave is the lack of a
commercially built remote tuner to handle that on 80 meters. It MUST be
tuned to some degree, if not entirely at the base of the wire. The SWR if
that is channeled in with coax to a tuner is outrageous otherwise.
Back to 160... I deliberately invoked the top of vertical current max,
in addition to the FCP, because I was trying to get every last shred of dB
to counter the PATHETIC performance of everything else I had tried for 160
in my property situation.
At that point I had simply thrown away all the conventional wisdom as
useless for my situation.
On Fri, Nov 9, 2012 at 8:52 PM, Mike Waters <mikewate@gmail.com> wrote:
> 84' + 104' ... I take it that's an inverted-L with a total length of 188'?
> That's interesting, Guy.
>
> I've been playing with different lengths of wire in EZNEC+ 5, for a 160
> Inverted-L here with a 55' high vertical section, and would appreciate some
> advice here. I'm leaning towards making mine longer than a 1/4 wavelength,
> too.
>
> My EZNEC models seem to indicate that lengthening the horizontal section
> --so that the total length of the inverted-l wire varies between 1/4 and
> 3/8 wavelength-- seems to make little difference in the low angle
> radiation; but the longer the wire, the more high-angle stuff there is.
>
> From what I can tell, lengthening the horizontal section will make very
> little difference in the gain at low angles for 160m DX. But the added
> high-angle radiation from a wire with a total length of from 5/16 to 3/8
> wavelength will improve the propagation for close-in contacts without
> affecting the DX capabilities.
>
> Am I wrong about this? Any comments on this would be very much appreciated.
>
> I haven't yet decided exactly how long to make my inverted-l yet, and I'd
> appreciate any advice. The constant is that the vertical portion will be
> 55' high, I am just undecided on how long to make the horizontal portion.
>
> I want to put the inverted-L back up very soon. I was going to use an FCP
> under this, but I'll probably just use elevated 1/4 wavelength radials like
> I did before.
>
> 73, Mike
> www.w0btu.com
>
> On Fri, Nov 9, 2012 at 6:59 PM, Guy Olinger K2AV <olinger@bellsouth.net
> >wrote:
>
> >
> > I'm using an FCP at 7 feet with an 84 foot vertical wire plus 104'
> > horizontal.
> >
> _______________________________________________
> Topband reflector - topband@contesting.com
>
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